Multi-Component Spectral Warping Analysis for Thin Bed Resolution

Abstract

A characteristic of a target layer is determined by receiving primary wave data and secondary wave data from multi-component receivers for acquiring both primary wave data and secondary wave data in a seismic exploration system, calculating a Vp/Vs ratio by correlating in a frequency domain a number of estimated primary wave spectra derived from a measured secondary wave spectrum to a measured primary wave spectrum, wherein Vp is a first velocity of a primary wave and Vs is a second velocity of a secondary wave for a target depth interval, using a warp factor associated with the Vp/Vs ratio, calculating a time separation for primary wave signals from a top and a bottom of the target depth interval.

What is claimed is: 
     
         1 . A method for determining a characteristic of a target layer, the method comprising:
 a computer receiving primary wave data and secondary wave data from multi-component receivers for acquiring both primary wave data and secondary wave data in a seismic exploration system;   the computer calculating a Vp/Vs ratio by correlating in a frequency domain a number of estimated primary wave spectra, derived from a measured secondary wave spectrum, to a measured primary wave spectrum, wherein Vp is a first velocity of a primary wave and Vs is a second velocity of a secondary wave for a target depth interval; and   the computer, using a warp factor associated with the Vp/Vs ratio, calculating a time separation for primary wave signals from a top and a bottom of the target depth interval.   
     
     
         2 . The method of  claim 1 , wherein the step of calculating the time separation for primary wave signals from the top and the bottom of the target depth interval further comprises:
 the computer identifying a trough in the measured secondary wave spectrum;   the computer identifying a frequency at a substantially lowest point of the trough;   the computer calculating a first time separation for the secondary signal by dividing the frequency into 1.0;   the computer calculating a second time separation by multiplying the first time separation by the warp factor; and   the computer using the second time separation, determining the characteristic of the target layer.   
     
     
         3 . The method of  claim 2 , wherein the characteristic is a thickness, and the target layer is a thin bed. 
     
     
         4 . The method of  claim 1  further comprising:
 the computer converting, by a first Fourier transform, the primary wave data in a time domain into a primary wave spectrum in a frequency domain; and 
 the computer converting, by a second Fourier transform, the secondary wave data in the time domain into a secondary wave spectrum in the frequency domain. 
 
     
     
         5 . The method of  claim 1 , wherein the step of the computer calculating the Vp/Vs ratio by correlating in the frequency domain the number of estimated primary wave spectra derived from the measured secondary wave spectrum to the measured primary wave spectrum, further comprises:
 the computer selecting the interval on the primary wave frequency spectrum;   the computer, creating the number of estimated primary wave frequency spectra using a warp factor;   the computer comparing each of the estimated primary wave frequency spectra with the actual primary wave spectra to obtain a number of correlation values, wherein each correlation value corresponds to one of the number of trial Vp/Vs values;   the computer plotting each of the number of correlation values against each of the number of trial Vp/Vs values;   the computer identifying a segment of the plot as a peak correlation;   the computer, responsive to identifying the segment of the plot as the peak correlation, identifying a trial Vp/Vs value that corresponds to the peak correlation; and   responsive to identifying the trial Vp/Vs value that corresponds to the peak correlation, designating the trial Vp/Vs value as the Vp/Vs ratio for the target depth interval.   
     
     
         6 . The method of  claim 5 , further comprising:
 calculating the warp factor using a formula 2/(1+(Vp/Vs))=α, where α is the warp factor, and each of a number of values for the warp factor are calculated using one of a number of trial Vp/Vs values, wherein the number of trial Vp/Vs values are selected from a range having an initial value and an end value and a number of substantially equidistant values between the initial value and the end value.   
     
     
         7 . A method for determining a characteristic of a target layer, the method comprising:
 a computer receiving primary wave data and secondary wave data from multi-component receivers for acquiring both primary wave data and secondary wave data in a seismic exploration system;   the computer calculating a Vp/Vs ratio by correlating in a frequency domain a number of estimated secondary wave spectra, derived from a measured primary wave spectrum, to a measured secondary wave spectrum, wherein Vp is a first velocity of the primary wave and Vs is a second velocity of the secondary wave for a target depth interval; and   the computer, using a warp factor associated with the Vp/Vs ratio, calculating a time separation for primary wave signals from a top and a bottom of the target depth interval.   
     
     
         8 . The method of  claim 7 , wherein the step of calculating the time separation for primary wave signals from the top and the bottom of the target depth interval further comprises:
 the computer identifying a trough in the measured secondary wave spectrum;   the computer identifying a frequency at a substantially lowest point of the trough;   the computer calculating a first time separation for the secondary signal by dividing the frequency into 1.0;   the computer calculating a second time separation by multiplying the first time separation by the warp factor; and   the computer using the second time separation, determining the characteristic of the target layer.   
     
     
         9 . The method of  claim 8 , wherein the characteristic is a thickness, and the target layer is a thin bed. 
     
     
         10 . The method of  claim 7 , further comprising:
 the computer converting, by a first Fourier transform, the primary wave data in a time domain into a primary wave spectrum in a frequency domain; and   the computer converting, by a second Fourier transform, the secondary wave data in the time domain into a secondary wave spectrum in the frequency domain.   
     
     
         11 . The method of  claim 7 , wherein the step of the computer calculating the Vp/Vs ratio by correlating in the frequency domain the number of estimated secondary wave spectra derived from the measured primary wave spectrum to the measured secondary wave spectrum, further comprises:
 the computer selecting an interval on the measured primary wave frequency spectrum;   the computer, creating a number of estimated secondary wave frequency spectra using a warp factor;   the computer comparing each of the number of estimated secondary wave frequency spectra with the measured secondary wave spectra to obtain a number of correlation values, wherein each correlation value corresponds to one of the number of trial Vp/Vs values;   the computer plotting each of the number of correlation values against each of the number of trial Vp/Vs values;   the computer identifying a segment of the plot as a peak correlation;   the computer, responsive to identifying the segment of the plot as the peak correlation, identifying a trial Vp/Vs value that corresponds to the peak correlation; and   responsive to identifying the trial Vp/Vs value that corresponds to the peak correlation, designating the trial Vp/Vs value as the Vp/Vs ratio for the target depth interval.   
     
     
         12 . The method of  claim 11 , further comprising:
 calculating the warp factor using a formula 2/(1+(Vp/Vs))=α, where α is the warp factor, and each of a number of values for the warp factor are calculated using one of a number of trial Vp/Vs values, wherein the number of trial Vp/Vs values are selected from a range having an initial value and an end value and a number of substantially equidistant values between the initial value and the end value.   
     
     
         13 . A computer system comprising one or more processors, one or more computer-readable memories, one or more computer-readable, tangible storage devices and program instructions which are stored on the one or more storage devices for execution by the one or more processors via the one or more memories and when executed by the one or more processors perform the method of  claim 1 . 
     
     
         14 . A computer system comprising one or more processors, one or more computer-readable memories, one or more computer-readable, tangible storage devices and program instructions which are stored on the one or more storage devices for execution by the one or more processors via the one or more memories and when executed by the one or more processors perform the method of  claim 7 . 
     
     
         15 . A computer program product comprising one or more computer-readable, tangible storage devices and computer-readable program instructions which are stored on the one or more storage devices and when executed by one or more processors, perform the method of  claim 1 . 
     
     
         16 . A computer program product comprising one or more computer-readable, tangible storage devices and computer-readable program instructions which are stored on the one or more storage devices and when executed by one or more processors, perform the method of  claim 7 .